The present invention relates to an apparatus and a method for thermal exhaust gas purification, in particular for purifying a mine exhaust gas or a mine exhaust, especially a methane-containing mine-ventilating gas. However, the present invention can also be used for thermal purification of other exhaust gases or exhausts containing flammable constituents, in particular volatile organic components (VOC).
It is known to use a thermal reactor for purifying mine exhaust gases, especially methane-containing mine ventilation gases (VAM), and to supply the hot gas produced during the thermal oxidation process to an energy recovery means. For example, CN 102733872 A proposes to utilize the heat energy of the hot gas to generate or further heat the water vapor which is used to drive a steam turbine coupled to a generator for generating electrical current.
The inventors have recognized that the energy efficiency of this process, as well as of many other heat exchange processes, is limited by the exclusive utilization of the calorific value (upper heating value) or the enthalpy difference between a heat exchange inlet temperature and a heat exchange outlet temperature. In many cases, utilization of the fuel value (lower heating value) of fuels or general utilization of the condensation energy of moist components of the (exhaust) gas is limited by the operating conditions of the secondarily generated energy form. This also applies, for example, to the generation of steam in the boiler operation of a power generation process.
Conventional methods (cf. e.g. CN 102733872 A) utilize the enthalpy difference of a hot gas stream heated by an upstream process for generating water vapor in the boiler operation. If such hot gas streams are produced in a combustion process of hydrocarbons or if these contain, for some other reason, larger amounts of condensable constituents, such as, for example, in a methane-containing mine ventilation gas, the condensation enthalpy is not utilized. On the contrary, in the case of larger amounts of water vapor in the gas stream, a disproportionately large quantity of the enthalpy inherent in the hot gas stream is bound in the form of evaporation enthalpy and thus is withdrawn from or not supplied to the energy transfer in the boiler.